Due to actualization of environmental problems in recent years, hybrid cars and electric cars have spread. Furthermore, as an air conditioner which is applicable to such a vehicle, there has been developed an air conditioner which comprises a compressor to compress and discharge a refrigerant, a radiator (a condenser) disposed on a vehicle interior side to let the refrigerant radiate heat, a heat absorber (an evaporator) disposed on the vehicle interior side to let the refrigerant absorb heat, and a refrigerant circuit constituted of an outdoor heat exchanger disposed outside the vehicle interior to let the refrigerant radiate or absorb heat, and which changes and executes respective modes such as a heating mode in which the refrigerant discharged from the compressor radiates heat in the radiator and the refrigerant by which heat has been radiated in this radiator absorbs heat in the outdoor heat exchanger, a dehumidifying mode in which the refrigerant discharged from the compressor radiates heat in the radiator and the refrigerant by which heat has been radiated in the radiator absorbs heat in the heat absorber, and a cooling mode in which the refrigerant discharged from the compressor radiates heat in the outdoor heat exchanger and absorbs heat in the heat absorber (e.g., see Patent Document 1).
Additionally, in Patent Document 1, there is disposed an injection circuit which distributes the refrigerant flowing out from the radiator, decompresses this distributed refrigerant, performs heat exchange between this refrigerant and the refrigerant flowing out from the radiator, and then returns the refrigerant to the middle of compression by the compressor in the heating mode, whereby the refrigerant to be discharged from the compressor is increased, and a heating capability by the radiator improves.